As I said a few days back, I thought it best to begin by addressing some of the terminology involved. I was browsing the web the other day to look for a good take on what the optokinetic and vestibulo-ocular reflexes are, and I came across Dr. Jeff Pelz's site which I thought does a good job of explaining things well.
It all comes down to the fact that the human eye makes many involuntary movements simply to create the pictures that we see when we look at something. Just as there are reflex arcs to involuntarily move your finger quickly away from a hot stove, there are reflexes within the eye to make sure the perceived vision is both stable and suitable to be interpreted.
Because humans evolved to develop eyes that both attempt to increase the field of vision and the resolution of what is seen, and because neither one of these is more developed than the other, as is the case with hawks or rabbits, our eyes have to be rapidly moved around a scene in order to get a clear and accurate picture of what is going on. This rapid movement is the reason we have the visual reflexes in question.
Any vision system relies first upon being able to move the eyes from one point to another quickly, and in fact this movement in humans is among the fastest possible by the human body, and are called saccadic movements. Once we can move the eyes, we can then turn our attention to getting a good image, and that's where two reflexes are involved. The optokinetic reflex stabilizes images that are blurred as a result of a moving field of vision. The best example I've heard of this occurs while driving down a road flanked by lampposts. The ability to follow one lamppost as it moves past you, then visually latch on to another one that is in front of you and follow it, is an example of the optokinetic reflex at work.
The vestibulo-ocular reflex (VOR) is similar to the optokinetic reflex, but is used for stability in the cases of a moving point of vision. This is the reflex used to account for head movements, and is the reason why you can read a book during a bumpy car ride. The VOR is the reason you could read this text and retain focus even if you were moving your head rapidly from side to side (if you're going to try that, be careful, it can induce headaches).
So when it comes down to it, these reflexes are important because they serve as corrective measures, and without them we would definitely not be able to see things as clearly as we can.
Many thanks go to Dr. Pelz, whose website I have paraphrased from extensively in this post. I would highly recommend reading it for a more in-depth look and application of what I have mentioned here.
Hopefully by next time I'll have found something in the news relating to these two reflexes. As always, comments are welcome.
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2 comments:
After viewing the post a few days back, I decided to test this "reflex" myself. In the passenger seat, while driving, I looked through the side window and tried to set my focus several meters out, to where the trees were. I realized I wasn't able to keep my eyes stationary; instead they kept jerking, trying to keep up with a specific location. I think this reflex is very interesting. Is it possible to be impaired by this reflex? Is there any technology based off of optokinetic reflexes?
Sunny: I think your reaction is because of your eyes trying to find something to focus on in a rapidly-moving field of vision. You were likely expressing some form of the optokinetic reflex when you focused on something, only to have it fly past you, at which point your eyes attempted to focus on something else.
Impairments are certainly possible, and that's discussed in more detail in the "Nystagmus" post. As far as technology goes, I know that the Rochester Institute of Technology has a visual lab, but I am not sure that there are many other technological applications of the reflexes.
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